The cellular data connectivity of mobile telephones and similar devices can be harnessed by other devices that do not have cellular data capabilities, such as personal computers (PCs), laptops and the like, by “tethering” the mobile telephone to the other device via a wired or wireless connection which enables the other device to make use of the mobile telephone's cellular data connectivity, for example to access the internet.
FIG. 1 is a schematic functional block diagram of a communications device such as a mobile telephone. As can be seen from FIG. 1, the device 10 includes a WLAN (wireless local area network) sub-system 12, which in normal operation of the device 10 is configured to operate in a wireless station (STA) mode.
The device 10 also includes a cellular modem 14, by means of which the device can connect to a cellular telecommunications network. Applications 16 executing on the device can access the internet through either the cellular network via the cellular modem 14 or through a wireless (e.g. WiFi®) network via the WLAN sub-system 12, depending upon the available connections and upon user preferences defined in a user configuration 18. A connection selector 20 connects the applications 16 to either the WLAN sub-system 12 or the cellular modem 14 via a respective Internet Protocol (IP) stack 22, 24 to permit transfer of data between the internet and the applications 16 over either the cellular network or the wireless network.
Typically when a user wishes to use the data connectivity of a mobile telephone or similar device to access the internet using another device such as a personal computer, tablet computer or the like, the mobile telephone must be manually placed into a mode commonly called “Hotspot”, “Personal Hotspot” or “Tethering” mode, and a connection must be established between the mobile telephone and the other device, typically by entering a password into one or both of the devices in response to a prompt.
FIG. 2 is a schematic functional block diagram of the communications device 10 of FIG. 1 configured for use in this tethering mode. In this mode, the WLAN subsystem 12 of the device 10 is placed into an Access Point (AP) mode and networking is set up within the device 10 through an IP router 30 of the device 10 to bridge data between the cellular modem 14 and the WLAN subsystem 12. The device 10 thus acts as a WLAN access point, and permits data flow between devices connected to this WLAN access point and the cellular network serving the device 10.
One field in which use of such tethering is increasing is in vehicles. Vehicle information and entertainment systems increasingly offer users access to the internet, via a tethered mobile telephone or other device, as schematically illustrated in FIG. 3. In such systems a head unit 40 installed in the vehicle acts provides wireless connectivity and internet access (via the tethered device) for user devices such as personal computers and tablet computers within the vehicle.
In the system illustrated in FIG. 3, a device such as a user's device 10 is tethered to the head unit 40 as described above, to provide access to the internet via its cellular modem 14. Thus, when the mobile device 10 is tethered to the vehicle head unit 40, its WLAN subsystem 12 is configured to operate in AP mode to act as a wireless access point, permitting access to the internet by the head unit 40 and any other device (e.g. device 70) that is connected to the head unit 40.
In addition, the head unit 40 may also provide wireless connectivity for devices associated with the vehicle, such as parking sensors, reversing cameras, display screens and the like, to permit such devices to communicate with each other and with other systems of the vehicle.
To facilitate this dual connectivity, the head unit 40 includes two WLAN subsystems. A first WLAN subsystem 42 is configured to operate in STA mode to act as a wireless station (STA), communicating with the WLAN subsystem 12 of the tethered device 10 (which, as indicated above, is configured to operate in AP mode to act as a wireless access point). A second WLAN subsystem is configured to operate in AP mode to act as a wireless access point, and to communicate with other devices 70 within the vehicle. An IP router function 46 of the head unit 40 is configured to bridge IP data between the other devices 70 and the tethered device 10, via IP stacks 48, 50, to permit internet connectivity for the other devices 70 via the cellular modem 14 of the tethered device 10.
The tethering method and system described above with reference to FIGS. 1 to 3 suffers from a number of disadvantages. Firstly, as described above, the user must manually configure the device 10 to operate in its tethering mode, and must manually configure the head unit 40 to connect to the device 10. As well as being tedious and time-consuming, in automotive applications of the kind described above there is an additional safety concern, as manually setting the device 10 to the tethering mode and connecting it to the head unit 40 of the vehicle may distract the driver's attention from the road.
Additionally, when the WLAN subsystem 12 of the device 10 is in the AP mode, it must be permanently on, which consumes a large amount of power compared to when the WLAN subsystem 12 operates in STA mode. As will be appreciated, this has a detrimental effect on the battery life of the device 10.
Accordingly, a need exists for an improved method of tethering a device such as a mobile telephone to another device to permit access by the other device to a data network.